Horned Armadillos and Rafting Monkeys: The Fascinating Fossil Mammals of South America

By Darin A. Croft and Velizar Simeonovski

A thrilling guide to the Cenozoic mammals of South America, featuring seventy-five life reconstructions of extinct species, plus photos of specimens and sites.

South America is home to some of the most distinctive mammals on Earth—giant armadillos, tiny anteaters, the world’s largest rodent, and its smallest deer. But the continent once supported a variety of other equally intriguing mammals that have no close living relatives: armored mammals with tail clubs, saber-toothed marsupials, and even a swimming sloth. We know of the existence of these peculiar species thanks to South America’s rich fossil record, which provides many glimpses of prehistoric mammals and the ecosystems in which they lived.

Organized as a “walk through time” and featuring species from fifteen important fossil sites, this book is the most extensive and richly illustrated volume devoted exclusively to the Cenozoic mammals of South America. The text is supported by seventy-five life reconstructions of extinct species in their native habitats, as well as photographs of fossil specimens and the sites highlighted in the book. An annotated bibliography is included for those interested in delving into the scientific literature.

“Well-written and easy for the nonspecialist to understand, this is also a most needed updating of this subject, much in the line of classic works such as Simpson’s The Beginning of the Age of Mammals in South America and Patterson and Pascual’s The Fossil Mammal Fauna of South America.” —Richard Fariña, coauthor Megafauna: Giant Beasts of Pleistocene South America

“This handsome book, written by a leading expert in South American paleontology, is profusely illustrated with maps, time charts, color photographs of fossils, and exquisite life reconstructions. The book . . . will appeal to any individual, young and old alike, interested in the fossil record, as well as to students and scholars of paleontology who work in other parts of the globe.” —Choice

• Language: English
• Publisher: Open Road Integrated Media
• Release date: Aug 29, 2016
• ISBN: 9780253020949

Book preview

Horned Armadillos and Rafting Monkeys

Horned Armadillos and Rafting Monkeys

The Fascinating Fossil Mammals of South America

DARIN A. CROFT

Illustrated by Velizar Simeonovski

Life of the PastJames O. Farlow, editor

This book is a publication of

Indiana University Press

Office of Scholarly Publishing

Herman B Wells Library 350

1320 East 10th Street

Bloomington, Indiana 47405 USA

iupress.indiana.edu

© 2016 by Darin A. Croft

All rights reserved

No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage and retrieval system, without permission in writing from the publisher. The Association of American University Presses’ Resolution on Permissions constitutes the only exception to this prohibition.

The paper used in this publication meets the minimum requirements of the American National Standard for Information Sciences–Permanence of Paper for Printed Library Materials, ANSI Z39.48-1992.

Manufactured in China

Cataloging information is available from the Library of Congress.

ISBN 978-0-253-02084-0 (cloth)

ISBN 978-0-253-02094-9 (ebook)

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TO ANYONE WHO HAS EVER WONDERED

WHAT A NOTOUNGULATE LOOKED LIKE.

Here is indeed an interesting mixture of creatures, and it takes only a modicum of human curiosity to want to know their history and to learn, as far as possible, how that mixture arose.

GEORGE GAYLORD SIMPSON,

Splendid Isolation: The Curious History

of South American Mammals

Contents

Preface

Acknowledgments

1. Time and Geography

2. Introduction to Mammals

Part I

Early South American Phase and Trans-Atlantic Dispersal Interval (TADI)

3. Tiupampa, Bolivia

3.1 Pucadelphys andinus

3.2 Mayulestes ferox

3.3 Molinodus suarezi

3.4 Alcidedorbignya inopinata

4. Itaboraí, Brazil

4.1 Epidolops ameghinoi

4.2 Colbertia magellanica

4.3 Protolipterna ellipsodontoides

4.4 Carodnia vieirai

5. Gran Barranca, Argentina

5.1 Sebecus icaeorhinus

5.2 Niolamia argentina and Caroloameghinia mater

5.3 Utaetus buccatus

5.4 Thomashuxleya rostrata

5.5 Notopithecus adapinus

6. La Gran Hondonada, Argentina

6.1 Otronia muhlbergi

6.2 Pseudhyrax eutrachytheroides

6.3 Puelia plicata

6.4 Trigonostylops wortmani

Part II

Late South American Phase

7. Tinguiririca, Chile

7.1 Klohnia charrieri

7.2 Pseudoglyptodon chilensis

7.3 Andemys termasi

7.4 Santiagorothia chiliensis

8. Salla, Bolivia

8.1 Paraborhyaena boliviana

8.2 Branisella boliviana

8.3 Anayatherium fortis

8.4 Trachytherus alloxus

8.5 Pyrotherium romeroi

9. Chucal, Chile

9.1 Parapropalaehoplophorus septentrionalis

9.2 Peltephilus ferox

9.3 Theosodon lallemanti

9.4 Nesodon imbricatus

9.5 Altitypotherium chucalensis

10. Santa Cruz, Argentina

10.1 Necrolestes patagonensis

10.2 Borhyaena tuberata

10.3 Hapalops indifferens

10.4 Steiromys duplicatus

10.5 Thoatherium minusculum

10.6 Interatherium robustum

11. La Venta, Colombia

11.1 Neotamandua borealis

11.2 Cebupithecia sarmientoi

11.3 Megadolodus molariformis and Purussaurus neivensis

11.4 Miocochilius anamopodus

11.5 Granastrapotherium snorki

12. Quebrada Honda, Bolivia

12.1 Acyon myctoderos

12.2 Hondalagus altiplanensis

12.3 Guiomys unica

12.4 Hemihegetotherium trilobus

13. Arroyo Chasicó, Argentina

13.1 Protomegalonyx chasicoensis

13.2 Prolagostomus and Lycopsis viverensis

13.3 Neobrachytherium ullumense

13.4 Chasicotherium rothi

13.5 Typotheriopsis chasicoensis

Part III

The Great American Biotic Interchange (GABI) and the Interamerican Phase

14. Acre, Brazil

14.1 Neoglyptatelus originalis

14.2 Thalassocnus natans

14.3 Phoberomys burmeisteri

14.4 Trigodon

15. Catamarca, Argentina

15.1 Andalgalornis steulleti

15.2 Thylacosmilus atrox

15.3 Vassallia maxima and Argentavis magnificens

15.4 Pronothrotherium typicum

15.5 Cyonasua brevirostris

16. Chapadmalal, Argentina

16.1 Sparassocynus derivatus

16.2 Macroeuphractus outesi

16.3 Scelidotherium parodii

16.4 Platygonus marplatensis

16.5 Paedotherium typicum

17. Tarija, Bolivia

17.1 Cuvieronius hyodon

17.2 Glyptodon reticulatus

17.3 Doedicurus clavicaudatus

17.4 Megatherium americanum

17.5 Protocyon tarijensis and Glossotherium tarijense

17.6 Smilodon populator

17.7 Onohippidium devillei

17.8 Macrauchenia patachonica

17.9 Toxodon platensis

Further Reading

Appendices

Appendix 1. Alphabetical List of Species

Appendix 2. Families and Higher Taxonomic Groups

Appendix 3. Mammals of Tiupampa, Bolivia

Appendix 4. Mammals of Itaboraí, Brazil

Appendix 5. Middle Eocene (Barrancan) Mammals of Gran Barranca, Argentina

Appendix 6. Mammals of La Gran Hondonada, Argentina

Appendix 7. Mammals of Tinguiririca, Chile

Appendix 8. Mammals of Salla, Bolivia

Appendix 9. Mammals of Chucal, Chile

Appendix 10. Mammals of Coastal Santa Cruz, Argentina

Appendix 11. Mammals of La Venta, Colombia

Appendix 12. Mammals of Quebrada Honda, Bolivia

Appendix 13. Mammals of Arroyo Chasicó, Argentina

Appendix 14. Mammals of Acre (Brazil and Peru)

Appendix 15. Mammals of Catamarca, Argentina

Appendix 16. Mammals of Chapadmalal, Argentina

Appendix 17. Mammals of Tarija, Bolivia

Glossary

Index

Preface

SOUTH AMERICA HAS A RICH AND FASCINATING FOSSIL MAMMAL record, the best among Southern Hemisphere continents. Unfortunately, most of these mammals are virtually unknown to the general public and even many paleontologists. One reason for this is that many varied and abundant groups left no living representatives or even close relatives. This makes it is difficult to make definitive statements about the habits of these mammals or even imagine what they may have looked like. Because most of these groups were restricted to South America, only a few museums outside that continent have specimens of them on display, and this has further impeded awareness of them elsewhere.

I myself was almost completely ignorant of the marvelous mammals of ancient South America until I undertook a Ph.D. thesis studying extinct species from Chile. Once I became familiar with them, I was struck by how difficult it was for friends and family to relate to the animals I was studying. I would describe these animals as small hoofed mammals that were not closely related to cows or horses and may have resembled large rodents more than anything else. That description usually just confused things or resulted in a shift in conversation. I realized that it was impossible for most people to identify with these animals without accurate reconstructions of how they may have appeared in life and accessible information about the roles they filled in ancient ecosystems.

The aim of this book is to provide the reader with a compelling but understandable summary of the extraordinary diversity of extinct South American mammals. I begin by briefly discussing the geography and main groups of South American mammals in the first two sections. I then highlight several species (primarily mammals) at each of 15 particularly well known paleontological sites. These sites were chosen because they span the so-called Age of Mammals (the Cenozoic Era, the last 66 million years), are distributed throughout much of the continent, and have produced important fossils of extinct species. The appendices of this book provide additional information about these sites and their extinct animals. Appendix 1 is an alphabetical list of the species reconstructed in this book. Appendix 2 is a comprehensive classification of families and higher taxonomic groups that are mentioned. This appendix also notes which families are represented by life reconstructions and discussed in greater detail. Appendices 3–17 list the mammal species that have been found at each of the sites highlighted in this book. These lists include relevant citations from the scientific literature.

Most of the life reconstructions in this book are of single mammal species, but some include two species and/or a bird or reptile. Each reconstruction is accompanied by a succinct description of the animal’s habits and characteristics and basic information about it including (1) size; (2) ecological characteristics; (3) evolutionary relationships; and (4) the meaning of its scientific name. Size estimates for each species were taken from the scientific literature or calculated firsthand based on fossil remains or those of closely related species (see also chapter 2). Ecological characteristics mainly focus on locomotion and diet, whereas evolutionary relationships provide some idea of how the species is classified (see also appendix 2). Intended meanings of scientific names were taken directly from the original publication on the species, though for many species (particularly those named by Florentino Ameghino), the author provided no explicit justification for why the name was chosen. In such cases, I have attempted to deduce the intended meaning based on Greek and Latin roots and other information. Most reconstructions are accompanied by at least one photo of a fossil or modern specimen (or cast) that illustrates a particular aspect of anatomy discussed in the text. Further Reading includes an annotated list of relevant publications that should be consulted for additional information about the sites, species, and other topics discussed in this book. The glossary can be consulted for definitions of terms highlighted in bold in the text.

The life reconstructions of extinct species in this book were skillfully executed by Velizar Simeonovski and result from extensive discussions between Velizar and me about the possible appearance and habits of each species. In many cases, these reconstructions are based on closely related species that are known from more complete remains rather than the species recorded at a particular site. For each species, we inferred external characteristics such as hair color and length based on its presumed ecological adaptations as well as its living relatives (when possible). Each species has been depicted in an appropriate environment in terms of climate and general vegetation structure (e.g., forest or savanna), but the plants are not necessarily those that would have been present in the area at the time.

It is my hope that the walk through time provided by these snapshots of ancient South American mammals and their communities will engender a wider and deeper appreciation of the splendidly unique mammals that once called the continent home.

Acknowledgments

THIS BOOK WAS MADE POSSIBLE BY THE NATIONAL SCIENCE Foundation, which has supported my field and lab research and the development of the life reconstructions featured in this work. If you enjoyed reading this book and learning about South American mammals, please be vocal in your support of science in general and agencies such as the National Science Foundation in particular. Thanks also go to the editors with whom I worked at Indiana University Press, Robert Sloan and James Farlow, for providing ideas and input and for helping to bring this book to fruition.

Part of the inspiration for this book was George Gaylord Simpson’s Splendid Isolation: The Curious History of South American Mammals. This outstanding review of ancient South American mammals is still a great read today.

I am indebted to John Flynn and Andy Wyss for taking me on as a graduate student and for introducing me to the fascinating world of South American mammals. Since then, I have had the good fortune to spend many weeks with John and Andy hunting fossils in Chile, and they have continued to serve as valuable mentors and role models for me as my career has developed.

Much of the content in this book stems from my field experiences in Chile and Bolivia. Accordingly, I would also like to acknowledge the National Geographic Society and the Chilean Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT), which have supported this research along with the NSF. I also thank the many students and colleagues with whom I have worked in Bolivia, Chile, and elsewhere for their enthusiasm and support, particularly our long-term collaborator in Chile, Reynaldo Charrier, and my long-term collaborator in Bolivia, Federico Anaya.

I have not yet been able to visit many of the field sites highlighted in this book. As a consequence, photos of them were graciously supplied by the colleagues whose names are listed in the captions. I very much appreciate their willingness to contribute to this volume.

All of the photographs of specimens in this book are from exhibits or research collections at the following institutions: American Museum of Natural History (New York), Arizona Museum of Natural History (Mesa), Cleveland Museum of Natural History, the Field Museum (Chicago), Florida Museum of Natural History (University of Florida, Gainesville), Museo Argentino de Ciencias Naturales (Buenos Aires), Museo de La Plata (La Plata, Argentina), Museo Nacional de Historia Natural (La Paz, Bolivia), Museo Nacional de Historia Natural (Montevideo, Uruguay), Museo Nacional de Historia Natural (Santiago, Chile), Museo Paleontológico Egidio Feruglio (Trelew, Argentina), Museum of Paleontology (University of California, Berkeley), Universidad Autónoma Tomás Frías (Potosí, Bolivia), University of Kansas Natural History Museum (Lawrence), and Yale Peabody Museum (New Haven). I thank these institutions for allowing me to study these collections and for playing a critical role in preserving them for future generations.

I am fortunate to have far too many academic friends and colleagues to be able to list here. However, Susi Bargo, Mariano Bond, Alejandro Kramarz, Guillermo López, Marcelo Reguero, and Sergio Vizcaíno made me feel particularly welcome when I first visited Argentina as a graduate student and helped convince me that South American mammals were more intriguing than those of any other continent. Colleagues such as these continue to make South America a great place to study paleontology.

Russell Engelman, who was an undergraduate at my home institution during development of this book, served as fact-checker and proofreader extraordinaire and was a consistent source of ideas and motivation during development of this project. I have collaborated with Russell on several research projects and look forward to continuing to work with him in the future.

I would be remiss if I did not acknowledge several individuals who encouraged me to pursue paleontology as a career from an early age. My parents were unwavering in their belief that I could do whatever I wanted and that if I were dedicated enough, everything would work out in the end. So far, they have been right, and I am glad I followed their advice.

I first got hooked on fossil collecting courtesy of my third-grade teacher, Arlene Christofferson, who included a unit on fossils in her curriculum and explained to me and my parents where we could collect 300-million-year-old horn corals. Although I now look for bones rather than corals, the exhilaration of finding a great specimen remains the same.

Between my junior and senior years of high school, I took a short course on mammalian paleobiology taught by Matt Joeckel at the University of Nebraska. This experience opened my eyes to the fact that extinct mammals could be just as fascinating as dinosaurs. As a consequence, my focus shifted toward a career in paleomammalogy. Matt’s enthusiasm illustrates the impact a good teacher can have on a student, even with a relatively brief interaction.

Finally, this project would not have been possible without the support, encouragement, and forbearance of my wife, Lisa, who also helped ensure that the text was suitable for nonexperts. I am certain she is as pleased as anyone that this project is complete.

Horned Armadillos and Rafting Monkeys

Geologic time scale of the Cenozoic Era illustrating South American Land-Mammal Ages (SALMAs), the four main phases of Cenozoic South American mammal evolution (numbered), and the three main intervals of faunal exchange: FABI (First American Biotic Interchange), TADI (Trans-Atlantic Dispersal Interval), and GABI (Great American Biotic Interchange).

1Time and Geography

Geologic Time

THE CENOZOIC ERA, THE MAIN FOCUS OF THIS BOOK, IS DIVIDED into three periods: the Paleogene, Neogene, and Quaternary (Fig. 1.1). Each of these, in turn, is divided into smaller units known as epochs. The Paleogene includes, from oldest to youngest, the Paleocene, Eocene, and Oligocene epochs. The Neogene includes the Miocene and Pliocene, and the Quaternary includes the Pleistocene and Holocene. Since epochs can span up to 18 million years, it is often useful to subdivide them using the terms early, middle, and late. These descriptors are technically defined, and all epochs except the shortest ones, the Pleistocene and Holocene, have early and late subdivisions. (Formal subdivisions of the Pleistocene are currently being discussed.) Three of the longer epochs, the Paleocene, Eocene, and Miocene, also have a middle interval. One can therefore speak of a middle Miocene but not of a middle Oligocene. (Epochs are also subdivided into smaller units known as stages or ages, but those are not addressed here.)

Paleomammalogists (paleontologists who study mammals) use another set of terms to refer to geologic time in addition to epochs: land-mammal ages. Unlike geologic units, land-mammal ages and similar systems vary from continent to continent; their divisions do not correspond in name, age, or duration. Consequently, I will mainly use geological units when discussing geological time and will mention corresponding South American Land-Mammal Ages (SALMAs) only in passing. SALMAs have long been used when speaking of extinct South American mammals, and although they are not emphasized here, it is necessary to have a general understanding of them in order to read the scientific literature on this topic.

Present and Past Geography of South America

South America is a long, relatively narrow continent mainly located in the Southern Hemisphere (see p. 5). Its northern edge lies just north of 12° N latitude and its southern tip sits at 56° S latitude, a distance of nearly 5,000 miles (8,000 km). Its broadest point is a bit south of the equator, where it is more than 3,000 miles wide (5,000 km). The continent narrows to the north and south of this point, with the southern extension being much longer and more gradually tapered. Thus, much of the continent is relatively narrow, especially the part in temperate latitudes known as the Southern Cone. The westernmost point of South America is located almost due south of eastern Ohio, meaning that the bulk of South America lies to the east of North America (other than Greenland).

The most conspicuous geographic feature of South America is the Andes Mountains. Aconcagua, in western Argentina, rises to an elevation of nearly 23,000 feet (7,000 m), making it the highest mountain outside the Himalayas. The Andes are the longest mountain chain in the world and run along the entire western edge of the continent, following the curve of the northern coastline of South America to the east. This huge mountain chain and a large latitudinal span that straddles the equator have created a wide variety of climates and habitats in South America. In the southern part of the continent, known as Patagonia, a narrow strip of temperate rainforest exists west of the Andes, while dry plains predominate to the east. This trend is reversed farther north, where deserts predominate west of the Andes in northern Chile and Peru, and the eastern slope of the Andes and the great Amazon Basin receive abundant moisture. Most of the northern third of South America receives abundant precipitation. On top of this general pattern, regional variation in soils and topography, proximity to the ocean, and seasonal variation in energy from the sun combine to create nearly every type of habitat one can imagine. Such habitats range from nearly lifeless deserts that have received no precipitation within recorded history to the most species-rich rainforests in the world, some of which receive up to 30 feet (10 m) of precipitation each year.

South America is presently connected to North America via the Isthmus of Panama, but this continuous land connection between the two continents has existed in its present form only for a few million years. Prior to this time, most groups of South American mammals were found nowhere else. Visiting South America would have been like visiting present-day Australia or Madagascar. Some mammals might have resembled those found in North America or Africa but would have been only distantly related. Other mammals would be truly unique. This uniqueness was characteristic of South American mammal communities as early as the mass extinction at the end of the Cretaceous Period (66 million years ago). South America was likely connected by land to both North America and Antarctica at this time; Antarctica was not yet covered by ice and was also connected to Australia. As a result, early Cenozoic mammal communities in South America included a mixture of Northern Hemisphere mammals as well as Southern Hemisphere ones. The exchange of mammal species among these continents around the time of the Cretaceous-Paleogene extinction has recently been termed the First American Biotic Interchange or FABI. This event set the stage for the evolution of South American mammals over the next 66 million years. The term FABI parallels the name coined several decades earlier for an equally important event in the history of South America, the Great American Biotic Interchange (GABI)–the large-scale exchange of mammals and other animals that was facilitated by the formation of the Panamanian land bridge in the late Cenozoic.

Between the FABI and the GABI, there was no major exchange of mammals between South America and any other land mass. This is because both of South America’s land connections were severed during the early Cenozoic. However, two mammal groups appeared in South America near the middle of the Cenozoic: rodents and primates (monkeys). Fossils indicate that both of these groups had an African origin. The most likely scenario to explain their appearance in South America is that they traversed the Atlantic Ocean on a floating island of vegetation expelled from the mouth of an African river after a storm. Upon landing in South America, they were able to found new populations of rodents and primates. Incredible as this might seem, it is not unprecedented. Such floating islands are known to occur today, and African mammals evidently reached the island of Madagascar in a similar fashion. What makes these South American dispersals so unusual is the distance involved; some 870 miles of ocean (1,400 km) separated Africa and South America at the time. Based on the fossil record, rodents made the crossing at least 40 million years ago. The arrival time of primates is less certain, but the oldest South American primate fossils are probably 35–30 million years old. The timing and duration of what could be called the Trans-Atlantic Dispersal Interval, or TADI, continues to change as new fossils are discovered, particularly in tropical areas.

Map of South America.

Using the FABI, TADI, and GABI as guides, the history of South American mammal communities can be divided into three intervals. These three intervals have been recognized in one form or another for many decades, though their boundaries have shifted based on new discoveries and remain somewhat blurry. During the first interval, the Early South American Phase, South American mammal communities consisted of endemic South American mammals as well as mammals with links to Australia-Antarctica and North America. The vast majority of groups with strong links to other continents declined and went extinct during the Paleocene and Eocene. Therefore, Oligocene and Miocene communities consist almost entirely of endemic South American mammal groups–including rodents and primates, which diversified there during this time. The interval spanning the Oligocene and Miocene has been termed the Late South American Phase. The beginning of this phase originally coincided with both the TADI and the Eocene-Oligocene boundary, but as the start of the TADI has been pushed into the Eocene, the initiation of this phase has become linked to the beginning of the Oligocene. Nevertheless, TADI mammals (rodents and primates) are only characteristic of Late South American Phase mammal communities. The GABI initiated the third interval of South American mammal communities, which is marked by major mixing of North American and South American groups. As a result, many groups of mammals are found in South America for the first time at sites of this age. Even though the GABI began in the Miocene, I include only mammal communities of Pliocene and Pleistocene age in the Interamerican Phase, since this is when North American mammals are abundant and diverse in South American faunas.

A fourth and final interval can be added to the traditional three-phase scheme described above, the Hypoamerican Phase. This interval is characterized by an extinction that eliminated the last representatives of many groups of South American mammals that had existed there since the Early South American Phase. This extinction coincides with the arrival of humans (Homo sapiens) in South America, and various lines of evidence suggest humans were at least partly responsible for it. For better or worse, the character of South American mammal communities changed dramatically during the Hypoamerican Phase, resulting in the mammal communities we know today.

2Introduction to Mammals

Mammal Classification

IF YOU HAVE TAKEN A BIOLOGY CLASS, YOU ARE PROBABLY ALREADY familiar with the seven main ranks in the hierarchical classification of life: kingdom, phylum, class, order, family, genus, and species. Many other ranks fall in between these main ranks, most formed by adding a prefix to indicate whether it is slightly more inclusive (higher in the hierarchy) or less inclusive (lower in the hierarchy). For example, a subclass is below a class, and a superorder is above an order. This book will focus on the class Mammalia (mammals) but will also discuss members of a few other classes. Within Mammalia, the most important ranks are orders and families. Orders are the main types of mammals, such as rodents, primates, and bats. Families are the primary subdivisions of orders and often correspond to familiar groupings. For example, cats (family Felidae), dogs (family Canidae), and bears (family Ursidae) are a few of the families that comprise the order Carnivora. Similarly, deer (family Cervidae), antelope (family Bovidae), and hippos (family Hippopotamidae) are a few of the families that comprise the order Artiodactyla. In mammals, family names usually end in the suffix -idae.

Body Size

Body size (typically measured as body mass) is one of the most fundamental characteristics of any mammal. Lifespan, metabolic rate, number of offspring, and home range size are just a few of the many attributes that correlate with body mass. Estimating the body mass of an extinct species is generally done by measuring a feature that correlates with body mass in living mammals, such as the length of the second molar or the diameter of the upper leg bone (femur), and inserting that value into a regression equation based on data from living species. This often generates a reasonably accurate body mass for the extinct species (one that is thought to be within 30% of its true body mass). Although this is straightforward in principle, it can be challenging in practice. For example, if